In the study, we tried to evaluate the effects of morphine injected through the systemic or neuraxial route on immune cell function and cytokine production in healthy women.In total, 29 paired samples of fresh peripheral blood were collected from healthy women who had been administered morphine for anesthetic analgesia through intravenous (IV), epidural, or spinal route postpartum. Their isolated peripheral blood mononuclear cells were mitogen-activated and stained with fluorochrome-conjugated anti-CD4, anti-CD8, anti-interleukin (IL)-2, and anti-interferon (IFN)-γ antibodies for flow cytometry, and the plasma levels of cytokines, including IL-6, IFN-α2, IL-10, IL-8, GM-CSF, and monocyte chemoattractant protein (MCP)-1, were measured through enzyme-linked immunosorbent assay.The results demonstrated that regardless of the administration route, morphine delivery slightly reduced IL-2 expression in CD4 cells after activation, and the same effect was not noted for CD8 cells. Intravenous or epidural morphine tended to reduce IFN-γ expression in CD8 cells. Spinal and IV morphine substantially increased IL-6 production, whereas epidural morphine hindered IL-10 and GM-CSF production. IV morphine injection reduced MCP-1 production in plasma. Compared with spinal morphine, IV or epidural morphine may more effectively inhibit the expression of various cytokines and thus affect immune response.All 3 routes of morphine injection tended to decrease IL-2 production by CD4 cells, whereas IV or epidural morphine injection showed lower IFN-γ production by CD8 cells. However, additional large-scale studies with longer follow-up durations are warranted.